Merge pull request #118 from astrojuanlu/make-tle-predictor-pickleable

Make TLEPredictor pickleable

.github/workflows/python-package.yml

@@ -30,7 +30,7 @@ jobs:
         if [ $(python -c "import sys; print(sys.version[:3])") != 3.4 ]; then python -m pip install --prefer-binary --editable .[fast]; fi
     - name: Lint with flake8
       run: |
-        flake8 orbit_predictor
+        flake8 orbit_predictor tests
     - name: Test with pytest
       run: |
         pytest -v --cov-report= --cov=orbit_predictor tests/

orbit_predictor/predictors/accurate.py

@@ -45,7 +45,6 @@
 """
 import datetime as dt
 from functools import lru_cache
-import warnings
 
 from sgp4 import ext, model
 from sgp4.api import Satrec, SGP4_ERRORS
@@ -88,6 +87,22 @@ def __init__(self, sate_id, source):
         self._sate_id = sate_id
         self._source = source
         self.tle = self._source.get_tle(self.sate_id, dt.datetime.utcnow())
+        self._propagator = self._get_propagator()
+
+    def _get_propagator(self):
+        tle_line_1, tle_line_2 = self.tle.lines
+        return Satrec.twoline2rv(tle_line_1, tle_line_2, WGS84)
+
+    def __getstate__(self):
+        # See https://docs.python.org/3/library/pickle.html#handling-stateful-objects
+        state = self.__dict__.copy()
+        del state["_propagator"]
+        return state
+
+    def __setstate__(self, state):
+        # See https://docs.python.org/3/library/pickle.html#handling-stateful-objects
+        self.__dict__.update(state)
+        self._propagator = self._get_propagator()
 
     @property
     def sate_id(self):
@@ -97,19 +112,6 @@ def sate_id(self):
     def source(self):
         return self._source
 
-    @reify
-    def _propagator(self):
-        tle_line_1, tle_line_2 = self.tle.lines
-        return Satrec.twoline2rv(tle_line_1, tle_line_2, WGS84)
-
-    @reify
-    def propagator(self):
-        warnings.warn(
-            "The .propagator property will be made private in a future release",
-            DeprecationWarning
-        )
-        return self._propagator
-
     @reify
     def mean_motion(self):
         """Mean motion, in radians per minute"""

tests/test_sources.py

@@ -92,8 +92,8 @@ def setUp(self):
 
         with open(self.filename, "w") as fd:
             fd.write(SATE_ID + "\n")
-            for l in SAMPLE_TLE:
-                fd.write(l + "\n")
+            for line in SAMPLE_TLE:
+                fd.write(line + "\n")
 
     def test_add_tle(self):
         db = sources.EtcTLESource(self.filename)

tests/test_sun.py

@@ -139,5 +139,5 @@ def test_ltan_from_raan(when_utc, raan, ltan):
     [winter_equinox, 180, 12],
     [winter_equinox, 270, 18],
 ])
-def test_ltan_from_raan(when_utc, raan, ltan):
+def test_raan_from_ltan(when_utc, raan, ltan):
     assert pytest.approx(raan_from_ltan(when_utc, ltan), abs=1/3600) == raan

tests/test_tle_predictor.py

@@ -22,6 +22,9 @@
 
 import datetime as dt
 import unittest
+import os
+import pickle
+import tempfile
 from unittest.mock import patch
 
 from orbit_predictor.coordinate_systems import llh_to_ecef
@@ -201,6 +204,22 @@ def test_off_nadir_computable_and_reasonable(self):
         pass_ = self.predictor.get_next_pass(ARG, date)
         self.assertLessEqual(abs(pass_.off_nadir_deg), 90)
 
+    def test_tle_predictor_is_pickleable(self):
+        # See https://github.com/satellogic/orbit-predictor/issues/117
+        with tempfile.TemporaryDirectory() as tmpdir:
+            pickle_file = os.path.join(tmpdir, "predictor.pkl")
+            with open(pickle_file, "wb") as fp:
+                pickle.dump(self.predictor, fp)
+
+            with open(pickle_file, "rb") as fp:
+                predictor = pickle.load(fp)
+
+            when_utc = dt.datetime.utcnow()
+
+            assert predictor.tle == self.predictor.tle
+            assert predictor.mean_motion == self.predictor.mean_motion
+            assert predictor.get_position(when_utc) == self.predictor.get_position(when_utc)
+
 
 class OffNadirAngleTests(unittest.TestCase):
     def setUp(self):